1. Field of the Invention
The invention relates to a chill casting wheel for the continuous casting of filamentary material. More particularly, the invention relates to casting wheels used to cast glassy metal filaments.
2. Description of the Prior Art
In the production of glassy alloy continuous filaments, typically an appropriate molten alloy is quenched at extreme quench rates, usually at least about 10.sup.4 .degree. C. per second by extruding the molten alloy from a pressurized reservoir through an extrusion nozzle onto a high speed rotating quench surface as is representatively shown in U.S. Pat. No. 4,142,571 for "Continuous Casting Method for Metallic Strips" issued Mar. 6, 1978 to Narasimhan, hereby incorporated by reference. Such filaments are necessarily thin, typically about 25-100 microns, due to the extreme heat transfer rate required to prevent substantial crystallization, though considerable selectivity may be exercised respecting the trans-dimensions and cross-section of the filament.
U.S. Pat. No. 4,307,771 for "Force-Convection-Cooled Casting Wheel" issued Dec. 29, 1981 to S. Draizen, et al. shows a casting wheel having a thick stiffening section which supports the quench surface and contains peripheral, drilled coolant passages located in proximity to the quench surface. The wheel is constructed to resist crowning-type distortions where the casting wheel radius at the quench surface edges becomes less than the wheel radius at the quench surface circumferential center line. When casting wide filaments greater than about 5 cm in width, however, such stiffened casting wheels do not provide sufficient crowning resistance.
Contoured quench surfaces have been used to address the crowning problem on rollers. However, casting wheels with contoured quench surfaces have been unsatisfactory because each particular contoured surface is effective only when specific use conditions of temperature and filament width are met. A variation in filament width, extrusion temperature or filament quench rate prevents the contoured surface from properly compensating for crowning-type distortions. Other problems with contoured quench surfaces include the cost and difficulty of initially machining the complex contours on the casting wheel quench surface and of periodically refurbishing the quench surface to maintain the precise contour.
Thus, ordinary casting wheels remain susceptible to crowning-type distortion problems, especially when wider filaments are cast. The wheels are difficult to refurbish and are unable to satisfactorily cast filaments having varied widths or requiring varied quench rates.